AAPT Loot: Color Ball

If you have been to an American Association of Physics Teacher conference, you have been to the exhibit hall. As long as I can remember,Educational Innovations has had a table there selling stuff. Awesome stuff that doesn’t cost too much. I like to bring back L00t for my kids when I go away. Shirts and city-based items usually are just dumb. However, if I can get one of these ‘toys’ that are also cool, it is win-win.

Here is the item I purchased (it was fairly cheap also – under $7, I think):

Big deal. It is a dumb old ball (that is probably what one of my daughters would say). But wait. There is a little knob on the bottom. Turn it on and it glows. Oh, Educational Innovations calls this the “Mystery Glowing Ball”. Although their website has some nice videos, I made my own – but it kind of sucks. Here are two screen shots so you can get the basic idea (or watch the video if you are really bored):

The image on the left is a composite of several frames of the video where I am spinning the ball around in a circle. On the right is the ball in a stationary state. Basically, it is a ball with three flashing lights inside it. These red, green, and blue lights alternate in their flashing. So simple but so cool.

Why do I like this device? I like it because besides being cheap, I can think of a couple cool things to do with it.

Combining colors of light

This is traditionally a difficult idea for some students (I talked about this some in the post how do color filters work). What happens when you combine red, green, and blue colors of light? The problem is that many people have experience combining colors of paint, but not light. A typical answer is that red + green + blue light gives some type of brownish color. You can set up three projectors with different filters on them, but it never works as well as I would like. This ball does the trick. Clearly the ball looks white-ish and not brownish. If students move it around quite fast, they can see that it is in fact red, green and blue.

Strobe motion kinematics

Take a look at the circle motion image above. If you know the frequency that the lights flash, you could make a time-exposure image for this thing. Boom. There you have some select points in time at different positions.

I tried to throw the ball and get a nice trajectory shot, but I didn’t have the camera at the right angle. This should be quite easy to accomplish though. So, you could throw it straight up, or at an angle. You can obviously spin it around in a circle.

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